The present invention relates to a telephone handset for a standard corded telephone (in the following designated telephone handset), a cordless telephone or a mobile telephone of the type described in the introductory part of claim 1.
Telephone handsets, cordless telephones and especially mobile telephones have gradually become so small and compact that sound problems very often occur, in particular in the low frequency range, that is below about 1 kHz. This is caused by the fact that it for the user of small, compact telephones, where the earcap plane or earpiece often do not have the most ideal shape, it may be difficult to avoid reduced sound quality, because the bass range is liable to disappear, if the earpiece is not held close against the ear, that is if too big leakages occur between the ear and the telephone or the telephone handset, respectively.
In general telephone handsets or similar acoustic apparatuses, which are acoustically connected to the surroundings in order to obtain independency of the variable acoustic leakage, must necessarily have a considerable lower acoustic impedance in the acoustic connection between the ear and the surroundings than that of the variations of the acoustic leakages in order to ballance these. On the other hand this also causes a considerable lower acoustic impedance against external noise sources.
The invention has for its purpose to provide a telephone handset, a cordless telephone or a mobile telephone, by which it by means of simple provisions becomes possible to compensate for the said sound problems in the low frequency range caused by the normal occuring leakages between the ear and the telephone or the telephone handset, respectively
The telephone handset, the cordless telephone or the mobile telephone according to the invention is distinctive in that a number of acoustic connections to an interior cavity and further on to normal occuring leakages of the handset or the telephone are provided in said earcap plane or earpiece in such a manner, that said connections are positionedxe2x80x94outside the ring-shaped gasket and preferably outside the circumference of the transducer but inside a diameter determined by the ear represented by a standardized measuring ear, that is inside a diameter of preferably 25 mm. By simple provisions possibillity to compensate for leakages between the ear and the telephone or the telephone handset, respectively, is hereby obtained, so that it becomes possible as well during measuring and in use to obtain a low acoustic output-impedance by an interaction between a transducer with adjusted frequency characteristic and an earcap plane or an earpiece with said acoustic connections to the interior cavity of the telephone handset, the cordless telephone or preferably the mobile telephone.
It should be pointed out that the current configuration of said connections, holes or apertures in the earcap plane or the earpiece to the interior cavity of the handset, the cordless telephone or the mobile telephone may be chosen quite arbitrary. It should furthermore be mentioned that in connection with future type approvals of mobile telephones as a demand may be measured with a new type 3.2 measuring ear instead of the present type IEC 318 measuring ear. However, for both measuring ears apply that use are made of coupling pieces with a diameter of 25 mm to form the connection to the earpiece.
In that period where both types of measuring ears in the principle may be required used by the type approval of a certain telephone handset, a certain cordless telephone or a certain mobile telephone it may be actual to use two different variants of transducers and two different designs of earpiecesxe2x80x94but of course in principle with the same construction.
Appropriately the handset, the cordless telephone or the mobile telephone according to the invention is such provided, that said acoustic connections in the earcap plane or the earpiece consist of circular apertures.
Or the telephone handset, the cordless telephone or the mobile telephone according to invention may advantageously be such modified that said acoustic connections in the earcap plane or the earpiece consist of narrow rectilinear and/or arched slits, which may form logo of a certain manufacturer.
Preferably the telephone handset, the cordless telephone or the mobile telephone according to the invention is furthermore such modified that said acoustic connections are made resistive (ohmic) preferably by application a netting (mesh) onto said inner wall of the earcap plane or the earpiece. In a particular simple manner a quite resistive acoustic connection between the earpiece and the interior cavity of the telephone handset, the cordless telephone or the mobile telephonexe2x80x94with that purpose to obtain a more optimized frequency caracteristicxe2x80x94is hereby obtained.
With particular advantage the telephone handset, the cordless telephone or the mobile telephone according to the invention in addition may be such modified that said acoustic connections and/or sound apertures of the earcap plane or the earpiece are provided in shape or pattern together with recesses in such a manner, that connections, apertures and recesses preferably in general form company logos of manufacturers of telephone handsets, cordless telephones or mobile telephones.
Alternatively the telephone handset, the cordless telephone or the mobile telephone according to the invention may be of the type where the earcap plane or the earpiece is placed on the internal side of a turnable flap, which from a closed inactive position, where the flap for instance covers the keyboard and the display, and which flap being adapted to be turned out to an active position, where the earcap plane or the earpiece may be pressed against the ear, said telephone handset, cordless telephone or mobile telephone being distinctive in that the transducer is built-in in the flap in such a manner, that the back of the transducer has one or more acoustic connections out through the back of the flap.
By this alternative embodiment it may in particular be appropriate, if the transducer is built-in in the flap in such a manner, that a passage through the flap to the open air is provided in the earcap plane or the earpiece outside the transducer but within said diameter represented by said standardized measuring ear.